Index: generic/tcl.decls
==================================================================
--- generic/tcl.decls
+++ generic/tcl.decls
@@ -2564,10 +2564,16 @@
 
 # TIP 651
 declare 685 {
     Tcl_Obj *Tcl_DStringToObj(Tcl_DString *dsPtr)
 }
+
+# TIP 660
+declare 686 {
+    int Tcl_GetSizeIntFromObj(Tcl_Interp *interp, Tcl_Obj *objPtr,
+	    Tcl_Size *sizePtr)
+}
 
 # ----- BASELINE -- FOR -- 8.7.0 / 9.0.0 ----- #
 
 declare 688 {
     void TclUnusedStubEntry(void)

Index: generic/tcl.h
==================================================================
--- generic/tcl.h
+++ generic/tcl.h
@@ -415,12 +415,12 @@
 #define Tcl_WideAsDouble(val)	((double)((Tcl_WideInt)(val)))
 #define Tcl_DoubleAsWide(val)	((Tcl_WideInt)((double)(val)))
 
 #if TCL_MAJOR_VERSION < 9
     typedef int Tcl_Size;
-#   define TCL_SIZE_MODIFIER ""
 #   define TCL_SIZE_MAX INT_MAX
+#   define TCL_SIZE_MODIFIER ""
 #else
     typedef ptrdiff_t Tcl_Size;
 #   define TCL_SIZE_MAX PTRDIFF_MAX
 #   define TCL_SIZE_MODIFIER TCL_T_MODIFIER
 #endif /* TCL_MAJOR_VERSION */

Index: generic/tclDecls.h
==================================================================
--- generic/tclDecls.h
+++ generic/tclDecls.h
@@ -2047,11 +2047,13 @@
 /* 684 */
 EXTERN int		Tcl_GetWideUIntFromObj(Tcl_Interp *interp,
 				Tcl_Obj *objPtr, Tcl_WideUInt *uwidePtr);
 /* 685 */
 EXTERN Tcl_Obj *	Tcl_DStringToObj(Tcl_DString *dsPtr);
-/* Slot 686 is reserved */
+/* 686 */
+EXTERN int		Tcl_GetSizeIntFromObj(Tcl_Interp *interp,
+				Tcl_Obj *objPtr, Tcl_Size *sizePtr);
 /* Slot 687 is reserved */
 /* 688 */
 EXTERN void		TclUnusedStubEntry(void);
 
 typedef struct {
@@ -2772,11 +2774,11 @@
     int (*tcl_GetNumber) (Tcl_Interp *interp, const char *bytes, ptrdiff_t numBytes, void **clientDataPtr, int *typePtr); /* 681 */
     int (*tcl_RemoveChannelMode) (Tcl_Interp *interp, Tcl_Channel chan, int mode); /* 682 */
     Tcl_Size (*tcl_GetEncodingNulLength) (Tcl_Encoding encoding); /* 683 */
     int (*tcl_GetWideUIntFromObj) (Tcl_Interp *interp, Tcl_Obj *objPtr, Tcl_WideUInt *uwidePtr); /* 684 */
     Tcl_Obj * (*tcl_DStringToObj) (Tcl_DString *dsPtr); /* 685 */
-    void (*reserved686)(void);
+    int (*tcl_GetSizeIntFromObj) (Tcl_Interp *interp, Tcl_Obj *objPtr, Tcl_Size *sizePtr); /* 686 */
     void (*reserved687)(void);
     void (*tclUnusedStubEntry) (void); /* 688 */
 } TclStubs;
 
 extern const TclStubs *tclStubsPtr;
@@ -4177,11 +4179,12 @@
 	(tclStubsPtr->tcl_GetEncodingNulLength) /* 683 */
 #define Tcl_GetWideUIntFromObj \
 	(tclStubsPtr->tcl_GetWideUIntFromObj) /* 684 */
 #define Tcl_DStringToObj \
 	(tclStubsPtr->tcl_DStringToObj) /* 685 */
-/* Slot 686 is reserved */
+#define Tcl_GetSizeIntFromObj \
+	(tclStubsPtr->tcl_GetSizeIntFromObj) /* 686 */
 /* Slot 687 is reserved */
 #define TclUnusedStubEntry \
 	(tclStubsPtr->tclUnusedStubEntry) /* 688 */
 
 #endif /* defined(USE_TCL_STUBS) */

Index: generic/tclObj.c
==================================================================
--- generic/tclObj.c
+++ generic/tclObj.c
@@ -3549,10 +3549,35 @@
 }
 
 /*
  *----------------------------------------------------------------------
  *
+ * Tcl_GetSizeIntFromObj --
+ *
+ *	Attempt to return a Tcl_Size from the Tcl object "objPtr".
+ *
+ * Results:
+ *  TCL_OK - the converted Tcl_Size value is stored in *sizePtr
+ *  TCL_ERROR - the error message is stored in interp
+ *
+ * Side effects:
+ *	The function may free up any existing internal representation.
+ *
+ *----------------------------------------------------------------------
+ */
+int
+Tcl_GetSizeIntFromObj(
+    Tcl_Interp *interp, /* Used for error reporting if not NULL. */
+    Tcl_Obj *objPtr,	/* The object from which to get a int. */
+    Tcl_Size *sizePtr)  /* Place to store resulting int. */
+{
+    return Tcl_GetIntFromObj(interp, objPtr, sizePtr);
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
  * FreeBignum --
  *
  *	This function frees the internal rep of a bignum.
  *
  * Results:
@@ -4052,11 +4077,11 @@
 	numBytes = 0;
     }
     if (numBytes < 0) {
 	numBytes = (ptrdiff_t)strlen(bytes);
     }
-    if ((size_t)numBytes > INT_MAX) {
+    if (numBytes > INT_MAX) {
 	if (interp) {
             Tcl_SetObjResult(interp, Tcl_ObjPrintf(
                     "max size for a Tcl value (%d bytes) exceeded", INT_MAX));
 	    Tcl_SetErrorCode(interp, "TCL", "MEMORY", NULL);
 	}

Index: generic/tclStubInit.c
==================================================================
--- generic/tclStubInit.c
+++ generic/tclStubInit.c
@@ -2055,11 +2055,11 @@
     Tcl_GetNumber, /* 681 */
     Tcl_RemoveChannelMode, /* 682 */
     Tcl_GetEncodingNulLength, /* 683 */
     Tcl_GetWideUIntFromObj, /* 684 */
     Tcl_DStringToObj, /* 685 */
-    0, /* 686 */
+    Tcl_GetSizeIntFromObj, /* 686 */
     0, /* 687 */
     TclUnusedStubEntry, /* 688 */
 };
 
 /* !END!: Do not edit above this line. */